The proposed research deals with the cellular mechanism for the renal excretion of organic anions. The major focus of research will be placed on: 1) characterizing the binding of 2,4,5-trichlorophenoxyacetate (2,4,5-T), an organic acid herbicide, to the cytosol, 2) exploring the possibility of labelling the membrane transport site by using various disulfonic stilbene derivatives as a chemical probe, and 3) exploring various techniques to separate the membrane proteins that are involved in the transport (or binding) of organic anions.